From the last few decades, there is a continuous increase in the demand of electrical power for various residential and industrial applications. Hence, the electrical systems are becoming increasingly complex, heavy, and powerful. A requirement of a high voltage electrical system is high voltage switching equipment. The high voltage switching equipment are used to control, protect and isolate electrical modules within the high voltage electrical system. The high voltage switching equipment have a property to act under special conditions. For example, high voltage switching equipment disconnect a section of the electrical system when flow of current goes beyond prescribed limits, which in turn protects the electrical system against damage.
A high voltage switching element used in the electrical systems may be a disconnector, circuit breaker, or a combination of disconnectors and circuit breakers. The most commonly used switching element is a circuit breaker. A circuit breaker is an electrical switch designed for making, carrying, and breaking a flow of normal as well as short circuit current.
High voltage circuit breakers may be used for controlling long transmission lines, (e.g., for extra high voltage electrical systems). The high voltage circuit breakers primarily have two pairs of contacts, (e.g., main contacts and resistor contacts). Functionally, the main contacts of the high voltage circuit breakers may be closed only after the resistor contacts are closed. FIG. 1 illustrates top view of a high voltage circuit breaker 100 in accordance with the state of the art. The high voltage circuit breaker 100 includes two interrupter units 102, 104 and two closing resistor units 106, 108. The high voltage circuit breaker 100 also includes a breaker tank 110. The high voltage circuit breaker 100 is connected between transmission lines, not shown in FIG. 1, such that current enters from the transmission lines in the high voltage circuit breaker 100 through an incoming terminal 112 and current exists from the high voltage circuit breaker 100 through an outgoing terminal 114. The incoming terminal 112 of the high voltage circuit breaker 100 is connected with the incoming interrupter unit 102 and the incoming closing resistor unit 106, as shown in FIG. 1. Additionally, the outgoing terminal 114 of the high voltage circuit breaker 100 is connected with the outgoing interrupter unit 104 and the outgoing closing resistor unit 108. The incoming interrupter unit 102 has an incoming main contact 118 and the outgoing interrupter unit 104 has an outgoing main contact 120. Similarly, the incoming closing resistor unit 106 has an incoming resistor contact 122 and the outgoing closing resistor unit 108 has an outgoing resistor contact 124, as illustrated in FIG. 1. The main contacts 118, 120 have fixed terminals 118A, 120A and moving terminals 118B, 120B, respectively. Also, the resistor contacts 122, 124 have fixed terminals 122A, 124A and moving terminals 122B, 124B, as shown in FIG. 1. When the moving terminals 118B, 120B, 122B, 124B move away from the respective fixed terminals 118A, 120A, 122A, 124A, respectively, then current stop flowing from the incoming terminal 112 to the outgoing terminal 114. The condition under which current stops flowing through the high voltage circuit breaker 100 is known as breaker open condition. The breaker tank 110, shown in FIG. 1, is a housing for mechanical linkages 116 that operates the main contacts 118, 120 and the resistor contacts 122, 124. The breaker tank 110 also holds the interrupter units 102, 104 and the closing resistor units 106, 108 together at an elevated height. The breaker tank 110 is supported by an insulated pole and a base along with a drive mechanism, not shown in FIG. 1. The drive mechanism derives the mechanical links 116 through the insulated pole.
During normal operation of the high voltage circuit breaker 100, the main contacts 118, 120 of the interrupter units 102, 104 are closed, e.g., the fixed terminals 118A, 120A and moving terminals 118B, 120B of the main contacts 118, 120 are in contact with each other. Also during normal operation, (e.g., when current is flowing though the high voltage circuit breaker 100), the resistor contacts 122, 124 of the closing resistor units 106, 108 are open, e.g., the fixed terminals 122A, 124A and moving terminals 122B, 124B of the resistor contacts 122, 124 are not in contact with each other. Under certain conditions, like faults or maintenance requirements, it is required to break the flow of current in some section or all sections of an electrical system. To break the flow of current, the main contacts 118, 120 of the high voltage circuit breaker 100 are needed to be opened, (e.g., breaker open condition that leads to restrict the flow of current from the incoming terminal 112 to the outgoing terminal 114), which in turn leads to the isolation of some section or all sections of the electrical system.
For the functioning of the electrical system, it is needed that all the sections of the electrical system should be electrically connected. Hence after the breaker open condition, once the fault is rectified or the maintenance is completed, then it is required to reconnect the main contacts 118, 120 of the high voltage circuit breaker 100 to resume the flow of current. According to the state of the art, a direct connection of the main contacts 118, 120 is avoided because a sudden connection of the main contacts 118, 120 over voltage condition due to switching transients, which might lead to complete breakdown of the electrical system. To avoid the effects of the switching transients, closing resistor units 106, 108 with the resistor contacts 122, 124 are provided. To resume the flow of current through the high voltage circuit breaker 100, it is recommended that closing of the main contacts 118, 120 should be followed by the closing of the resistor contacts 122, 124. The resistor contacts 122, 124 provide damping effect to over voltage arises due to switching transients, which leads an additional protection of for the high voltage circuit breaker 100.
FIG. 2 illustrates a circuit 200 of the high voltage circuit breaker 100. In the circuit 200, the main contacts 118, 120 and resistor contacts 122, 124 are represented as switches 118, 120, 122, 124 that are connecting the incoming terminal 112 and the outgoing going terminal 114 of the high voltage circuit breaker 100. All the switches 118, 120, 122, 124 of the circuit 200 are open, which represents the breaker open condition, as illustrated in FIG. 2. The circuit 200 also includes resistors R1, R2, R3, R4 providing resistance to the resistor contact units 106, 108. To resume the flow of current through the high voltage circuit breaker 100 after the breaker open condition, first the switches, (e.g., the resistor contacts 122, 124), are closed, which leads to a flow of current between the incoming terminal 112 and the outgoing terminal 114 through the resistors R1, R2, R3, R4 that provides a damping effect. After a pre-defined time delay, the switches, (e.g., the main contacts 118, 120), are closed after closing the switches 122, 124. Because of the closing of the switches, (e.g., the main contacts 118, 120), current started flowing between the incoming terminal 112 and the outgoing terminal 114 through the interrupter units 102, 104. Almost all current flows through the interrupter units 102, 104 instead of the closing resistor units 106, 108 because the interrupter units 102, 104 offer a less resistive path for current in comparison to the closing resistor units 106, 108. After stabilization of flow of current through the interrupter units 102, 104, the switches, (e.g., the resistor contacts 122, 124), are set to an open condition to make sure no current flow through the closing resistor units 106, 108.
The high voltage circuit breaker 100, illustrated in FIG. 1 and FIG. 2, needs a good amount of material for manufacturing due to the presence of multiple closing resistor units, which also increases the weight of the overall circuit breaker assembly. Due to high weight of the circuit breaker, it becomes problematic to keep the circuit breaker at an elevated height and it causes mechanical stability problems. Also, the time required to assemble the high voltage circuit breaker is also high because of the complexity of the circuit breaker due to the presence of multiple closing resistor units. Additionally, the circuit breaker, as disclosed in the state of the art, is susceptible to high risk of failure due to seismic load because of its complex design and weight. Further, due to the presence of multiple main and resistor contacts, high mechanical energy is required for operating the contacts because more number of contacts leads to more number of moving parts. In other words, high mechanical energy is required for the mechanical links 116, illustrated in FIG. 1, because the mechanical links 116 are operating the four moving terminals 118B, 120B, 122B, 124B.
From the above-mentioned problems associated with a circuit breaker, it is evident that there is a strong need of a less complex, light in weight, and easy to assemble circuit breaker.